Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
  • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
  • B01J2/04—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a gaseous medium
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K9/00—Medicinal preparations characterised by special physical form
  • A61K9/14—Particulate form, e.g. powders, Processes for size reducing of pure drugs or the resulting products, Pure drug nanoparticles
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D279/00—Heterocyclic compounds containing six-membered rings having one nitrogen atom and one sulfur atom as the only ring hetero atoms
  • C07D279/10—1,4-Thiazines; Hydrogenated 1,4-thiazines
  • C07D279/14—1,4-Thiazines; Hydrogenated 1,4-thiazines condensed with carbocyclic rings or ring systems
  • C07D279/18—[b, e]-condensed with two six-membered rings
  • C07D279/20—[b, e]-condensed with two six-membered rings with hydrogen atoms directly attached to the ring nitrogen atom
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K15/00—Anti-oxidant compositions; Compositions inhibiting chemical change
  • C09K15/04—Anti-oxidant compositions; Compositions inhibiting chemical change containing organic compounds
  • C09K15/30—Anti-oxidant compositions; Compositions inhibiting chemical change containing organic compounds containing heterocyclic ring with at least one nitrogen atom as ring member

Definitions

• Phenothiazine is an aromatic amine-based product used in a wide variety of applications, including as an inhibitor, antioxidant and short-stopping agent in a variety of diverse applications such as the stabilization of acrylic acids, esters and monomers or as a stabilizer for chloroprene monomer, styrene monomer and other vinylic monomers; as an antioxidant in synthetic lubricants and oils, in polyols for polyurethanes and polyester and vinyl ester resins; and as a pharmaceutical intermediate. Phenothiazine is typically manufactured in flake and powder forms and having a bright yellow appearance (indicating lack of oxidation).
• the flake form may be prepared by coating molten phenothiazine onto a drum flaker, whereupon it is cooled and crystallised into a thin layer which is scraped off as a mixture of flakes and fines (powder).
• the product is then conveyed to a physical separation (classification) process in which the fines (powder) are separated from the flakes, typically by the use of sizing screens.
• the flaked phenothiazine is then packaged and shipped to customers who convey or transfer this through their own processing equipment.
• the product generally contains up to about 6% of fines after manufacture.
• the flakes are prone to breakdown into fines during subsequent shipping and handling.
• Flaked products containing such fines suffer from the deficiencies of non- uniform particle size, caking, dustiness and clumping.
• Phenothiazine being a respiratory, skin, eye and gastrointestinal irritant and skin sensitizer, is more likely to cause problems in a finely-divided form. Fines in the flaked product also increase the likelihood of explosion.
• Flaked phenothiazine containing high levels of fines i.e., more than about 6% particles having diameters less than 500 microns is especially prone to caking or clumping.
• Non-uniform particle size in flaked phenothiazine increases the tendency of the product to cake and/or clump and to resist ready flow transfer both internally and at customer facilities.
• the caking and/or clumping makes it difficult to discharge the phenothiazine from containers such as bins, bags, trucks, storage silos and the like and difficult to transfer. It can also cause the formation of bridges or blocks in containers.
• Fines also present safety, health and environmental issues. From a safety standpoint, fines are of particular concern due to the increased risk of explosion, as well as increased risk to employee health, especially through skin irritation and skin sensitization and the like, as noted above.
• prilling towers are 80 to 300 feet in height and require large volumes of air.
• Drawbacks with conventional prilling technology include the fact that large towers and significant volumes of air are required. This requires high capital costs and significant operational costs.
• phenothiazine currently cannot be prilled by conventional technology as the product in molten state, reacts and undergoes oxidation, changing in both chemical composition and color.
• An oxidized form of phenothiazine is green to grey in color. This form is of differing chemical composition to the desired pure phenothiazine. Purified phenothiazine in a non-oxidized form is a bright yellow color.
• the melting temperature of phenothiazine is 184°C and, thus, its handling and transfer in the molten state is difficult. Pumping molten phenothiazine the 80 to 300 feet, as would be required to reach the top of a conventional prilling tower, is difficult without significant heat tracing of lines. If line temperatures drop below the melting point of the product, it quickly solidifies in the transfer line, causing operational difficulties.
• any new method produces a product which meets the industry-wide quality specification of > 99.6% phenothiazine in the product.
• color is also an important indicator of purity and it is highly desirable that the product color is from a pale-greenish-yellow through to bright yellow and especially is free from any grey or completely green material, which can adversely affect downstream applications, even if analytical purity is > 99.6%.
• Phenothiazine color is conveniently assessed by use of a Munsell Color Chart and it is highly desirable that the appearance of the product falls within the region of the Munsell Color Chart defined by Hue Symbol 5Y and Color Spaces: 8/4 to 8/12, 8.5/4 to 8.5/12 and 9/4 to 9/8, inclusive, and more especially in the region defined by Hue Symbol 5Y and Color Spaces 8.5/8 to 8.5/12 and 9/6 to 9/8.
• the invention includes solid phenothiazine or an analog or derivative thereof (as hereinafter described), comprising a plurality of prills, wherein said prills are generally spherical.
• phenothiazine refers to the compound of
• phenothiazine material refers generically to phenothiazine of Formula (I) and/or an analog or derivative of phenothiazine of Formula (II) (see below).
• the invention further includes a method of reducing the level of fines (powder) in phenothiazine material, comprising forming the phenothiazine material in prill form such that the prills have a generally spherical shape.
• the invention also includes solid phenothiazine material comprising a plurality of prills of phenothiazine material, wherein the prills are generally spherical and the product has no greater than about 6% by weight fines (i.e. particles with diameters ⁇ 500 ⁇ ).
• the invention includes a method for making prills of phenothiazine material comprising introducing molten phenothiazine material into at least one nozzle having a plurality of holes to form molten droplets of phenothiazine material and cooling the droplets to form solid prills, all within an inert environment.
• the method is especially suitable for making phenothiazine in the form of greenish-yellow to yellow prills.
• the invention also includes solid phenothiazine material formed by that method.
• the invention is directed to phenothiazine material having improved properties and reduced levels of fines (powder) which is in prill form as well as to a method for making the phenothiazine material in prill form.
• the invention is further directed to a method for reducing the level of fines in phenothiazine material while maintaining product quality.
• the phenothiazine material is phenothiazine.
• a solid phenothiazine material in the form of a plurality of generally spherical prills.
• the prill form preferably has a greenish-yellow to yellow color, more preferably a color within the region of the Munsell Color Chart defined by Hue Symbol 5Y and Color Spaces: 8/4 to 8/12, 8.5/4 to 8.5/12 and 9/4 to 9/8, inclusive, more especially in the region defined by Hue Symbol 5Y and Color Spaces: 8.5/8 to 8.5/12 and 9/6 to 9/8, inclusive. It is especially preferred that the phenothiazine prill-form has a bright yellow color, more especially a bright yellow color equivalent to that of flaked phenothiazine.
• the phenothiazine prill product preferably contains at least 99.6% phenothiazine.
• a method for making solid phenothiazine mate ⁇ al in prill form comprising breaking a stream of molten phenothiazine material into a plurality of evenly sized droplets and cooling the droplets to form solid phenothiazine material in the form of prills, the phenothiazine material being maintained within an inert gas (preferably nitrogen) environment while in the molten state. It is further preferred that the inert gas environment is maintained until the phenothiazine material, in prill form, has cooled to below about 140°C.
• an inert gas preferably nitrogen
• the prills may be formed by feeding molten phenothiazine material into at least one nozzle having a plurality of holes to form molten droplets of phenothiazine material which are cooled to form prill ⁇ .
• the molten phenothiazine material may be any available form of phenothiazine material, such as powder or flake.
• Phenothiazine is a solid material which is currently commercially available in both flake and powder forms.
• phenothiazine material may include any phenothiazine analog or derivative, provided it is in solid form and can be made to be in a molten form, for example through application of heat.
• Phenothiazine has a molecular weight of 199.26 and a chemical formula of C 12 H 9 NS.
• a typical commercially-available phenothiazine has a melting point of 184°C and a boiling point of 371 °C.
• the bulk density is about 0.85 for flake product and about 0.75 for powder.
• the chemical formula of phenothiazine is as follows:
• Phenothiazine material includes phenothiazine and its analogs and derivatives including, without limitation, compounds having formula (II):
• R 1 , R 2 , and R 3 may be the same or different and may be hydrogen; halogens, such as chlorine and fluorine and the like; branched or straight chain, and substituted or unsubstituted hydrocarbon groups such as alkyl, alkenyl, or alkynyl groups of from 1 to 26 carbon atoms; substituted and unsubstituted aryl groups and aralkyl groups; or functional groups, including, but not limited to sulfonyl, carboxy, amine, alkylamine, hydroxy, carboxy, silyl, siloxy; and other similar derivatives and their salts.
• Substituents for the aforementioned hydrocarbon, aryl and aralkyl groups may include any of the above functional groups as well as inter-chain elements such as oxygen, sulfur, silicon, nitrogen, and the like.
• R 1 , R 2 and R 3 in Formula (II) is hydrogen.
• m and n are preferably independently from about 1 to about 4.
• the phenothiazine material in molten form which may be phenothiazine in accordance with formula (I) and/or phenothiazine derivatives or analogs in accordance with formula (II), is fed into the nozzle chamber of a jet priller capable of receiving a molten phenothiazine material and passed through prilling nozzle(s) having a plurality of holes.
• FIG. 1 is a schematic representation of a jet priller and associated equipment suitable for making phenothiazine prills in accordance with the invention.
• a method for forming phenothiazine prills in accordance with the invention is described with reference to Fig. 1.
• Phenothiazine is conveniently converted into the molten state by heating, to a temperature from about 190°C to about 215°C, more preferably from about 205°C to about 215°C, in a Feed Tank (1 ) under an inert atmosphere (preferably nitrogen gas) provided from a pressurised Inert Gas Store (2).
• the molten mass is then transferred by pressure of inert gas to a Conditioning Vessel (3) where the temperature is adjusted to about 195-200°C.
• the inert gas (preferably nitrogen) pressure is maintained at about 1.5 to 3 bar in the Conditioning Vessel (3) in order to drive the molten phenothiazine into the Nozzle Chamber (5) of the Jet Priller (6) under a nitrogen atmosphere, via a Filter (4) to remove foreign material.
• the inert gas pressure in the Nozzle Chamber (5) is carefully controlled at a fixed pressure preferably between 0 and 1 bar, and more preferably from 0.035 to 0.80 bar, in order to control the flow rate of phenothiazine through the Prilling Nozzle (7).
• molten phenothiazine passes through the holes of the Prilling Nozzle (7), into the top of the Prilling Column (8), it is broken in a controlled manner into droplets of from about 1 mm to about 2 mm, by the action of a Vibrating Membrane (9) in the wall of the Nozzle Chamber (5) which is vibrated by Vibration Unit (10) operating at a frequency from about 100 to about 1500 Hz, more preferably from about 400 to about 1100 Hz.
• a stream of liquefied inert gas, especially liquid nitrogen, is simultaneously fed into the side of the Prilling Column (8) from a Liquefied Inert Gas Store (1 1 ) and the mixture of cold inert gas, in liquid and gaseous forms, quickly cools the small droplets of molten phenothiazine to generally spherical, prills.
• the use of cold inert gas, especially nitrogen, is important in order to maintain product quality and to achieve a greenish yellow to yellow colored product.
• phenothiazine prills may be used to form phenothiazine prills according to the invention, nitrogen is preferred, because it is so effective in rapidly cooling the prills and preventing any contact with an oxidising atmosphere, thus maintaining the preferred yellow color, especially a color in the range Hue Symbol: 5Y Color Space: 8/4 to 8/12, 8.5/4 to 8.5/12 and 9/4 to 9/8, inclusive.
• the droplets are cooled initially by the mixture of cold, gaseous and liquid inert gas (especially nitrogen) into partially crystalline prills as they fall through the Prilling Column (8).
• the prills reach the foot of the Prilling Column (8), they are generally at a temperature from about 120°C to about 170°C, more preferably about 140°C, from where they pass into a Spiral Cooler (12), having the form of a cyclone, wherein, the prills cool further in the cold inert gas environment, until crystallisation is complete, by the time they reach the bottom of the Spiral Cooler (12).
• the quality of the phenothiazine prills is sensitive to the relative flow rates of phenothiazine and inert gas.
• the flow rate of nitrogen through the Prilling Column (8) and Spiral Cooler (12) is preferably from 0.25 to 0.3 kg per kg of prilled phenothiazine.
• the inert gas, leaving the Spiral Cooler is drawn by a Fan (15) into a Cyclone (14) to remove fines and recycled into the Prilling Column (8) via a Cooler (16) to supplement the feed of fresh liquid nitrogen.
• a preferred jet priller is commercially available from GMF Gouda, Goudsche Machinefabriek, B.V. in Waddinzveen, Holland, sold as Model JP15 and prills can be manufactured using such a jet priller.
• Phenothiazine in prill form is useful for many applications, particularly those in which phenothiazine powder is problematic.
• the phenothiazine prills in accordance with the invention may be used in a wide variety of applications, including as a stabilizer for a variety of chemical applications.
• the product may also be used for an inhibitor, antioxidant and short-stopping agent in a variety of diverse applications such as the stabilization of acrylic acids, esters and monomers or as a stabilizer for chloroprene monomer, styrene monomer and other vinylic monomers.
• the prill product is also useful as an antioxidant in synthetic lubricants and oils, polyols for polyurethanes and polyester and vinyl ester resins.
• Phenothiazine material in prill form, is also a useful pharmaceutical intermediate.
• the prilled phenothiazine material of the invention preferably has less than about 6% and more preferably less than about 1 % by weight fines (powder), i.e. particles having diameters less than about 500 microns. Further, the prilled phenothiazine material preferably has an average diameter as measured in the longest dimension of the prill product from about 0.5 mm to about 2.3 mm and more preferably from about 1 mm to about 2 mm.
• the generally spherical prills of phenothiazine material in accordance with the invention have significantly improved flow characteristics due to their uniformity of size and are generally safer in use than standard phenothiazine material in flake or powder form.
• Example 1 Small-scale trial in a simulated laboratory-scale priller
• a one liter, 3-neck reactor flask was used to simulate a flaker feed tank. It was equipped with nitrogen feed, a stirrer for agitation, a temperature probe and a bottom outlet. The apparatus was vacuum evacuated and nitrogen purged three times prior to product loading under nitrogen. The reactor was then charged with phenothiazine flake which was heated under nitrogen to a molten state at about 200°C. The molten phenothiazine was then slowly dripped through the bottom outlet valve (a simulated nozzle) into approximately one liter of liquid nitrogen (at about -192°C) in a vacuum jacketed Dewar flask. Bright yellow prills were formed and subjected to selective analyses. The bright yellow prills met all product specifications, evidenced no precipitate, and handled in a similar manner and efficiency to standard phenothiazine flake.
• Phenothiazine flake was charged to a Feed Tank (1). The flake was then melted and conveyed at about 200°C, under 3.1 bars pressure, (nitrogen gas) to a Conditioning Tank (3). The product was then fed under nitrogen pressure into the Nozzle Chamber (5) of a Model JP15/1 Closed-Loop jet priller from GMF Gouda (6) having a Nozzle (7) with 100 holes each having a diameter of about 0.5 mm. The phenothiazine flow rate through the Nozzle (7) was controlled by maintaining a constant nitrogen pressure in the Nozzle Chamber (5).
• the product was broken into 1-2 mm droplets as it passed through the nozzle (7), by means of a Vibrating Membrane (9) in the wall of the Nozzle Chamber (5), controlled, with the aid of a stroboscope, at a frequency of 1005-1007 Hz.
• Prills were formed from the droplets by immediate liquid nitrogen cooling of the molten droplet into a solid prill form.
• the molten feed was at approximately 200°C (ranging generally from about 194.7 to 195.5°C) and the liquid nitrogen temperature was about -192°C.
• the flow rate of liquid nitrogen from Liquefied Inert gas Store (11) was varied from 0.25 kg of nitrogen per kg of prills to 0.30 kg of nitrogen per kg of prills.
• the prills as formed were generally sphe ⁇ cal in shape and had an average diameter of about 1 mm.
• the prills also had a low angle of repose and exhibited a very narrow particle size distribution.
• Low fines (powder) levels of less than 1% were achieved, and the product was not prone to caking.
• the product also evidenced flow, transfer and handling characteristics superior to the existing flake product. Additionally, due to the more uniform shape and smaller average particle size, the prills demonstrated an enhanced dissolution time in comparison to flake product.
• a comparison of the properties of standard flake and the prills formed in Example 2 are shown below in Table 1.
• prills of phenothiazine were formed which exhibited properties at least comparable, and in most cases superior to those of flaked and powdered phenothiazine.
• the prills also, advantageously, exhibited a substantially uniform average diameter and narrow particle size distribution as well as containing only a very low level of fines. Such characteristics provided reduced incidences of caking and/or clumping and demonstrated improved flow properties in transport and in use.
• Other significant advantages achievable by using these prills include improvements to environmental and workplace safety as well as a reduction in the cost of manufacturing resulting from the low level of fines.

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